Commonly owned German published specification No. DE-OS 32 00 832 describes an apparatus for wrapping a pallet load in such a hood which is slipped from above around the stack so that a lower marginal portion or rim projects below the underside of the pallet. With the pallet elevated above a supporting surface such as that of a conveyor, a suction fan is actuated to aspirate air from below the underside of the pallet so as to draw the surrounding marginal portion inward, causing it to fold around the pallet edge. This folding is assisted by a pair of bell cranks swinging horizontally on the conveyor, underneath diagonally opposite corners of the raised pallet, serving to smooth the bent-over rim of the hood.
After this wrapping operation, and with the fan still running, the pallet load is lowered onto the conveyor. Consequently, the folded rim becomes clamped between the pallet and the conveyor surface. Thereafter, the load is moved to a heating station in which the hood is thermally shrunk around the stack and the pallet, e.g. as described in my copending application Ser. No. 566,330 filed Dec. 28, 1983 (now U.S. Pat. No. 4,562,689).
Such a system has the disadvantage of utilizing two separate stations so that a considerable amount of space is required, aside from the necessary structures and control mechanisms. Furthermore, the overlapping layers of sheet material on the underside of the pallet are difficult to heat-seal to a satisfactory degree as these layers are not uniformly heated in their clamped position.